This invention is generally directed to processes for developing images; and more specifically the present invention is directed to an improved process for developing electrostatic latent images with a toner composition containing therein various low molecular weight wax compositions. Thus, in one embodiment of the present invention there is provided a process for the fixing of images in electrostatic imaging systems with a compliant fuser roll, such as a Viton fuser roll, wherein a release fluid including silicone oils is selected for the purpose of improving the fusing latitude, and release characteristics of the toner composition selected, which toner composition is comprised of resin particles, and certain additive waxes. Accordingly, the toner and developer compositions of the present invention are useful for enabling the development of images in electrostatographic systems, particularly those imaging systems wherein a compliant fuser roll is selected and reduced amounts of silicone oils are utilized.
Generally, prior art developer compositions selected for use in developing electrostatic images enable the toner image to be fixed to a permanent substract, such as paper, by contacting the paper with a roller, the surface of which is formed from a material capable of preventing toner particles from sticking thereto. Usually in this process, however, the surface of the fixing roll is brought into contact with the toner image in a hot melt state, thus a part thereof can adhere to and remain on the surface of this roll. This causes a portion of the toner image to be transferred to the surface of a subsequent sheet on which the toner image is to be successively fixed, thereby causing the well known undesirable offset phenomena.
For the purpose of substantially eliminating offsetting, and more specifically to prevent adhesion of the toner particles to the surface of the fixing means, there has been selected certain types of rollers, the surface of which may be covered with a thin film of an offset preventing liquid such as a silicone oil. These oils are highly effective, however, the apparatus within which they are incorporated is complicated and costly since, for example, a means for feeding the oil is required. Also, not only do the silicone oils emit an undesirable odor, they deposit on the machine components causing toner particles to collect on, and adhere to the silicone oils. An accumulation of toner particles on machine components is troublesome in that the image quality is adversely effected, and these components must be periodically cleaned and/or replaced, adding to the maintenance costs of the system involved.
One Viton fuser roll selected for use in electrostatographic copying machines is comprised of a soft roll fabricated from lead oxide, and duPont Viton E-430 resin, a vinylidene fluoride hexafluoropropylene copolymer. This roll contains approximately 15 parts of lead oxide, and 100 parts of Viton E-430, which mixture is blended and cured on the roll substrate at elevated temperatures. Apparently the function of the lead oxide is to generate unsaturation by dehydrofluorination for crosslinking, and to provide release mechanisms for the toner composition. Excellent image quality has been obtained with Viton fuser rolls, however, in some instances there results a toner fuser compatibility problem when charge control agents are part of the toner mixture. For example, it appears that certain specific charge control additives, such as quaternary ammonium compounds, and alkyl pyridinium compounds, including cetyl pyridinium chloride, react with the Viton of these fuser rolls. For example, cetyl pyridinium chloride when part of the toner mixture appears to be catalytically decomposed by the lead oxide contained in the fuser roll, resulting in a highly unsaturated compound, which polymerizes and condenses with the unsatured Viton E-430 material. In view of this, the Viton fuser roll turns black, develops multiple surface cracks, and the surface thereof hardens, thereby resulting in image quality deterioration.
Also, disclosed in a copending application, U.S. Ser. No. 434,198, entitled Positively Charged Toner Compositions, are toner compositions comprised of resin particles, pigment particles, a low molecular weight wax material, and a charge enhancing additive. These toner compositions are particularly useful in electrostatic imaging systems wherein an offset preventing fluid, such as a silicone oil, is not required. In contrast, in accordance with the present invention a reduced amount of offset preventing liquid is selected, and the fusing latitude temperature for the selected toner composition is desirably increased.
A substantial number of the electrostatographic imaging machines in commecial use incorporate therein various offset preventing liquids, such as silicone oils, and while these oils possess a number of disadvantages there have been developed compositions and processes wherein some of the disadvantages are eliminated. Therefore, the use of silicone oils in electrophotographic imaging systems continues to be viable, and thus processes which continue to use such oils are required. Additionally, there is a need for processes wherein the amount of silicone oil used an be reduced somewhat, and wherein the fusing latitude of the toner composition can be desirably increased. Furthermore, there continues to be a need for processes for developing images with a toner composition containing low molecular weight waxes and wherein there is selected a compliant fuser roll such as a Viton fuser roll. Also, there continues to be a need for imaging processes wherein soft compliant fuser rolls are selected, and the developer composition in addition to containing a low molecular weight wax has incorporated therein charge enhancing additives.